DEVELOPMENT OF CONCEPTACLE IN THE FUCACEJE. 39 
the usual law of division, the result is that it is bounded 
laterally (as in fig. 1) not only by cells of the limiting tissue 
(aussenriiide), but partly also by cells of the subjacent cortical 
tissue (innenrinde). 
Up to the stage represented in fig. 1 no important change 
is to be observed in the initial cell. It contains a nucleus 
and plentiful protoplasm, and its walls are normal. 
There may, however, be noticed at the apex the beginning 
of a separation of its cell-wall from those of the cells around 
it. In the latter the only modification of the usual divisions 
is an inclination of the vertical wails towards the initial 
cell. 
Conceptacles of this stage of development are to be found 
on the inner side of the lips bordering the terminal cavity of 
the fertile branch. 
Fig. 2 represents part of a vertical longitudinal section 
passing through a slightly older conceptacle. Here the 
initial cell has lost its internal tension. The cell-walls have 
collapsed, while the substance of the cell-walls themselves 
has been converted into the swollen mass which fills the 
cavity thus formed. This mass is continuous with the layer 
which covers the surface of the thallus ; it already shows 
signs of the change which it undergoes later. 
The upper part of the initial cell has shrivelled, and 
appears to have no cell contents ; the lower part, which 
adjoins the basal cell, still contains^ a small quantity of 
vacuolated protoplasm. The basal cell has meanwhile 
increased in size, but has not yet divided. If figs. 1 and 2 
are compared, it will not be difficult to assign their origin to 
the cells which border on the cavity in fig. 2.^ It will be 
seen that, as Heinke rightly observed (loc. cit., p. S87), they 
are of different origin. 
As foreshadowed in fig. 1, the cell- walls of the limiting 
tissue are strongly inclined in fig. 2 tOAvards the centre of 
the conceptacle. The group marked I being most so, it is 
between the group I and the group c that the boundary of 
origin of the tissues lies, the group I being derived from 
the limiting tissue, the group c by the division of a cell . 
of the cortical tissue. Those cells, then, which border the 
lower part of the cavity of the conceptacle (including the 
basal cell) are derived from the cortical tissue ; those which 
line the upper part from the limiting tissue. 
A surface-view of a conceptacle, intermediate in develop- 
‘ 1 do not mean to imply by such a comparison that the order of the cell 
divisions is constant. A mere glance at the figures will be sullicient to 
preclude such an idea, 
